Shell Coding Style

if and for statements like this:

  if true; then
          do something
  else
          do something else
  fi

  for i in a b c; do
          echo $i
  done

Use single quotes unless the string contains parseable content, e.g.;
```
  foo='bar baz boo'
  foo="$bar $baz $boo"
```
What about:
```
  `` vs $();
  source vs .;
  $foo vs ${foo} ?
```
- source is a bashism. ‘.’ is sh, but it’s easier to grep for source. Use source when the script is bash and you’re pretty sure it will stay bash, ‘.’ otherwise. ${foo} should only be used when it’s needed.